The present invention relates to a defect inspection method which optically inspects defects of a minute pattern or foreign matters formed on a sample through a thin film process typically included in a semiconductor manufacturing process or a flat panel display manufacturing process, and more particularly to a defect inspection method and its device including an illumination optical system which is suitable for detecting the minute defects or foreign matters.
WO 1999/006823 A (Patent Literature 1) discloses a conventional semiconductor wafer inspection device. This patent literature discloses a system for illuminating a laser beam linearly onto a wafer. As the illumination system, in the disclosed technique, the cylindrical lens or the main surface of the mirror is arranged, parallelly to the wafer, and the wafer is illuminated in a linear pattern.
JP 5-209841 A (Patent Literature 2) discloses a system for linearly illuminating the wafer. The literature discloses a technique for condensing a laser beam onto a diffraction grating and obliquely forming an image of the condensed light.